1. Field of the Invention
The present invention relates to a signal processing device and method and reception system and, more particularly, to a signal processing device and method and reception system capable of measuring the power spectrum of a signal having a large variation in power level with high accuracy.
2. Description of the Related Art
Television receivers and television program recorders have a channel scan function adapted to automatically detect the frequency bands used for television broadcasting channels.
Channel scan is achieved by obtaining the power spectrum of the input signal and extracting, for example, the frequencies at which the peak power spectra appear, as the center frequencies of the channels used for television broadcasting.
FIG. 1 is a diagram illustrating the configuration of a spectrum acquisition block in the related art.
A spectrum acquisition block configured as shown in FIG. 1 is incorporated in a television receiver or program recorder. During channel scan, the spectrum acquisition block measures the power spectrum of the input signal, followed by the extraction of the channels by the processing section at the subsequent stage based on the measured power spectrum.
As illustrated in FIG. 1, the spectrum acquisition block includes an amplification section 1 and spectrum measurement section 2. A frequency conversion block 11 and narrow band filter 12 are provided in the spectrum measurement section 2. The input signal obtained as a result of the reception of radio wave by the antenna is fed to the amplification section 1.
The amplification section 1 adjusts the power of the input signal to a level that can be handled by the spectrum measurement section 2 with its gain set to a fixed level. The same section 1 outputs the adjusted input signal to the spectrum measurement section 2.
In the spectrum measurement section 2, the frequency conversion block 11 converts the frequency of the input signal supplied from the amplification section 1. The signal converted in frequency passes through the narrow band filter 12 so that the power spectrum thereof is measured. The power spectrum shows the power levels of different frequency components.
In the spectrum measurement section 2, the frequency conversion block 11 successively measures the power spectra of the target frequencies while at the same time sweeping the frequencies (changing the target frequencies). The signal representing the power spectra measured by the spectrum measurement section 2 is supplied to the processing section at the subsequent stage.
[Patent Document 1]
Japanese Patent Laid-Open No. 2009-5352